In some ways, MDF is lousy stuff: You can ruin it with a single spilled cup of coffee, it doesn’t take fasteners well, it has virtually no structural properties and machining it kicks up a horrific amount of dust. However, those of you with shops likely have some MDF lying around. It can’t be beat for flatness, and while it swells slightly during summer and shrinks a bit during winter, it’s still plenty stable enough to yield a reliable jig. Or throw some veneer on top of it, support it properly and you can sneak it into low-cost furniture, as many do.